filter out -tryjob when finding vanilla image.

We cannot find vanilla image because the build name of trybot
image was falco-release-tryjob, it then tries to find vanilla
image of falco-release-tryjob, but it could not find it.

BUG=none.
TEST=vanilla image was found.

Change-Id: I9024ea27f480db70ae296012a5958d8e243f3c38
Reviewed-on: https://chromium-review.googlesource.com/786315
Commit-Ready: Yunlian Jiang <yunlian@chromium.org>
Tested-by: Yunlian Jiang <yunlian@chromium.org>
Reviewed-by: Yunlian Jiang <yunlian@chromium.org>
diff --git a/buildbot_test_toolchains.py b/buildbot_test_toolchains.py
index a274cc5..d8f9309 100755
--- a/buildbot_test_toolchains.py
+++ b/buildbot_test_toolchains.py
@@ -97,7 +97,9 @@
     Returns:
       Latest official image name, e.g. 'daisy-release/R57-9089.0.0'.
     """
-    mo = re.search(TRYBOT_IMAGE_RE, trybot_image)
+    # We need to filter out -tryjob in the trybot_image.
+    trybot = re.sub('-tryjob', '', trybot_image)
+    mo = re.search(TRYBOT_IMAGE_RE, trybot)
     assert mo
     dirname = IMAGE_DIR.replace('\\', '').format(**mo.groupdict())
     return buildbot_utils.GetLatestImage(self._chromeos_root, dirname)
@@ -121,7 +123,8 @@
       Corresponding chrome PFQ image name, e.g.
       'daisy-chrome-pfq/R40-6393.0.0-rc1'.
     """
-    mo = re.search(TRYBOT_IMAGE_RE, trybot_image)
+    trybot = re.sub('-tryjob', '', trybot_image)
+    mo = re.search(TRYBOT_IMAGE_RE, trybot)
     assert mo
     image_dict = mo.groupdict()
     image_dict['image_type'] = 'chrome-pfq'